What occurrence provides the climax for the story "An Occurrence at Owl Creek Bridge"?

Ambrose Bierce's short story "An Occurrence at Owl Creek Bridge" exudes drama as it tells the story of Peyton Farquhar, a planter escaping his execution with seemingly supernatural luck. This drama, however, comes to a head with the final, climactic moment of the piece. The climax of this story comes in the moment of Peyton's death, ripping him out of his dying fantasy.

As he is about to clasp [his wife], he feels a stunning blow upon the back of the neck; a blinding white light blazes all about him with a sound like the shock of a cannon—then all is darkness and silence!

The next paragraph in the story contains the last sentences in the piece, which reveal that all the events since the end of the first section are imagined by Peyton during the proceedings of his hanging.
Bierce includes several hints throughout the short story—each more disconcerting than the last—as to how the piece will end. Several of these hints come from the story's disorienting, inconsistent, and overly convenient events. For instance, the soldiers at the bridge are described as "unarmed" right before they all shoot at Peyton. Also, it would be a little too convenient for Peyton to successfully escape the ropes around his neck and hands, dodge barrages of shots, escape a whirlpool, find his way through sprawling nature in the dead of night, and walk home, asleep, without perishing from thirst or injuries.
The most interesting clue Bierce includes is the sudden change of verb tense at the end of Peyton's journey. As he miraculously arrives home, the story shifts from past to present tense as Peyton sees an idealized, dreamlike version of his life—with white walkways; the sweet, feminine presence of his wife; and his own overwhelming joy. This all sets the scene perfectly for an unexpected twist, and the reader is left heartbroken after the reveal that none of Peyton's great escape ever really happened.